Electrostatic chucks are heated to high temperatures in a semiconductor process and have a cooling plate for heat dissipation. In this case, the material of the electrostatic chucks may be alumina, the material of the cooling plate may be aluminum, and a resin may be used as a bonding material. There is a very large difference in linear thermal expansion coefficient between alumina and aluminum. For example, alumina has a linear thermal expansion coefficient of 7.9 ppm/K (RT-800° C.: Uchida Rokakuho “Seramikku no butsuri (Physics of ceramics)”), and aluminum has a linear thermal expansion coefficient of 31.1 ppm/K (RT-800° C.: “Shinpen netsubussei handobukku (Thermophysical properties handbook new edition)”, edited by Japan Society of Thermophysical Properties). In such electrostatic chucks, soft resins used as bonding materials can relieve stress resulting from a difference in linear thermal expansion coefficient. However, since resins are organic materials, resins have low heat dissipation ability, decompose easily at high temperatures, and tend to deteriorate over time. It is therefore difficult to use resins in a high temperature process for a long time. Thus, metal bonding was found to be effective as a heat dissipation bonding material that replaces resins. Bonding materials, such as aluminum, solder, and silver solder, are used in metal bonding. However, unlike resins, metals are stiff and cannot relieve stress resulting from a difference in linear thermal expansion coefficient between an electrostatic chuck and a cooling plate.
In metal bonding between an electrostatic chuck and a cooling plate, the characteristics required for the cooling plate include a small difference in linear thermal expansion coefficient from the electrostatic chuck, high thermal conductivity in order to maintain heat dissipation ability, high denseness that allows the passage of a coolant liquid or gas, and high strength that allows processing or installation. Patent Literature 1 discloses a composite material that can satisfy these characteristics to some extent. The composite material is a TiC-based Ti—Si—C composite material having a phase containing Ti3SiC2: 1.0% to 20.0% by volume, SiC: 0.5% to 8.0% by volume, and TiC as the remainder. Because of a small difference in linear thermal expansion coefficient between TiC and alumina, it is supposed that the Ti—Si—C composite material containing the TiC main phase described in Patent Literature 1 and alumina also have a small difference in thermal expansion coefficient.